Nitride-based semiconductor materials have high breakdown field strength and high electron mobility and thus are expected to be applied to power-electronics semiconductor devices, high-frequency power semiconductor devices, or the like.
In a horizontal power-electronics semiconductor device, it is preferable that a gate width be large for driving with a large current. At this time, a multi-finger structure is preferably used. Here, a horizontal power-electronics semiconductor device having a multi-finger structure has a large switching loss due to parasitic capacitance between interconnections and a substrate and thus there is a demand for a decrease in parasitic capacitance.